Methods and compositions for removing sulfur from liquid hydrocarbons using ammonium adducts

ABSTRACT

Improved desulfurization compositions are provided for removing substantial fractions of sulfur, sulfur complexes, and sulfur compounds from liquid hydrocarbons such as crude oil and fuels. The preferred compositions comprise amine adducts, such as the adduct formed by reacting benzoic acid and a fatty acid amine. The compositions may be contacted with liquid hydrocarbons in the presence of water to achieve high levels of desulfurization. Preferably, the compositions are added substantially continuously to a flowing stream of liquid hydrocarbon and water, e.g., to the output from a producing oil well or in pipeline transmission and/or refinery equipment.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is broadly concerned with desulfurization ofliquid hydrocarbon/water mixtures such as crude oils and derivativesthereof. More particularly, the invention is concerned with compositionswhich can be directly contacted with liquid hydrocarbons and water toeffect substantial desulfurization of the hydrocarbon fractions thereof,as well as methods of preparing and using the compositions. Thecompositions of the invention preferably are made up of solid or liquidmaterials including therein an amine adduct such as the adduct derivedfrom the reaction of coco-1,3-diaminopropane and an acid such as benzoicacid.

2. Description of the Prior Art

The concentration of sulfur in crude oil is typically between 0.05 and5.0% (by weight), although values as high as 13.95% have been reported.In general, the distribution of sulfur in crude oil is such that theproportion of sulfur increases along with the boiling point of thedistillate fraction. As a result, the higher the boiling range of thefuel the higher the sulfur content will tend to be. For example, amiddle-distillate-range fraction, e.g., diesel fuel, will typically havea higher sulfur content than the lower-boiling-range gasoline fraction.Upon combustion, the sulfur in fuels can contribute to air pollution inthe form of particulate material and acidic gases, such as sulfurdioxide. To reduce sulfur-related air pollution, the level of sulfur infuels is regulated, and to meet these regulations sulfur must be removedfrom fuels during the refining process.

Refineries remove organic sulfur from crude oil-derived fuels byhydrodesulfurization (HDS). HDS is a catalytic process that convertsorganic sulfur to hydrogen sulfide gas by reacting crude oil fractionswith hydrogen at pressures between 150 and 3,000 lb/in² and temperaturesbetween 290 and 455° C., depending upon the feed and level ofdesulfurization required. Organic sulfur compounds in the lower-boilingfractions of petroleum, e.g., the gasoline range, are mainly thiols,sulfides and thiophenes, which are readily removed by HDS. However,middle-distillate fractions, e.g., the diesel and fuel oil range,contain significant amounts of benzothiophenes and dibenzothiophenes(DBTs), which are considerably more difficult to remove by HDS. Amongthe most refractory of these compounds are DBTs with substitutionsadjacent to the sulfur moiety. Compounds of this type are referred to assterically hindered compounds because the substitutions are believed tosterically hinder access of the sulfur atom to the catalyst surface. Dueto their resistance to HDS, sterically hindered compounds represent asignificant barrier to reaching very low sulfur levels in middle- andheavy-distillate-range fuels. The high cost and inherent chemicallimitations associated with HDS make alternatives to this technology ofinterest to the petroleum industry. Moreover, current trends towardstricter regulations on the content of sulfur in fuels provide incentivefor the continued search for improved desulfurization processes.

Biodesulfurization has been studied as an alternative to HDS for theremoval of organic sulfur from fuels. The use of hydrocarbon degradationpathways that attached DBT were unsuccessful because these systemsrelied on the oxidation and mineralization of the carbon skeletoninstead of on sulfur removal and therefore significantly reduced thefuel value of the desulfurized end product. More recently, bacteria thatdesulfurize DBT and a variety of other organic sulfur compoundstypically found in petroleum oils via a sulfur selective oxidativepathway that does not remove carbon have been isolated. This pathwayinvolves the sequential oxidation of the sulfur moiety followed bycleavage of the carbon sulfur bonds.

Amine salts such as those formed by the reaction between acetic oracrylic acids and coco-1,3-diaminopropane have been used in the past ascorrosion inhibitors or biocides in producing wells. Such salts aretypically added in large amounts on an infrequent basis to producingwells to “shock” the system and serve as an effective biocide, or invery small quantities for corrosion inhibition purposes. In addition,amine salt corrosion inhibitors are commonly used with emulsionbreakers, in order to minimize any oil-water emulsions which caninterfere with effective inhibition. See, e.g., U.S. Pat. No. 5,427,999.Additional references include: U.S. Pat. Nos. 4,297,237; 5,322,630;2,995,603; 3,996,024; 5,019,361; 4,131,583; 5,032,318; 4,248,717;4,490,155; 4,290,900; 4,157,972; 4,011,882; 4,499,006; U.S. PatentPublication No. U.S. 2003/0200697; EPO Publications 256802 and 798364;and Japanese Publication No. EP97302039.

Despite all of these well-known desulfurization efforts, there stillexists a need for easy and cost-effective desulfurization of liquidhydrocarbons, using readily available components and a simplifiedremoval mechanism.

SUMMARY OF THE INVENTION

The present invention overcomes the problems outlined above and providescompositions effective for desulfurization of liquid hydrocarbons. Asused herein, desulfurization or removal of sulfur from hydrocarbonsrefers to the removal of any or all types of sulfur and sulfur-bearingspecies, e.g., elemental sulfur, sulfur complexes and the full gamut ofsulfur compounds found in hydrocarbons such as mercaptans andthiophenes.

As used herein, “alkyl,” whether referring to individual compounds or asmoieties of larger compounds, is intended to embrace both saturated andunsaturated species such as alkenyl and alkynyl compounds or groups, aswell as straight and branched chain compounds and species. Similarly,“aryl” is intended to embrace mono- or poly-ring compounds or moieties.

Broadly speaking, the treatment compositions of the invention includeadducts of secondary, tertiary, or quaternary mono- and polyamines andmixtures thereof. Preferred amines are of the formula:R—(NR₁—(CH₂)_(n)—NHR₂)_(x)wherein R is selected from the group consisting of aryl, alkyl,cycloalkyl, arylalkyl, alkoxyalkyl, hydroxyalkyl, and alkoxyhydroxygroups and wherein the alkyl groups or moieties are selected from theC2-C24 alkyls, R₁ and R₂ are individually selected from the groupconsisting of H and C1-C4 alkyls, n is from about 2-12, and x is fromabout 1-8. The most preferred amines for use in the invention are theC8-C24 fatty acid diamines such as cocodiamine and tallowdiamine.

The amines of the invention are reacted with an appropriate acid inorder to yield the adducts of the invention. A wide variety of acids canbe used in this context, but generally the acids employed should not besulfur-bearing. Exemplary acids include C2-C8 alkyl and aryl mono- andpolyorganic acids and derivatives thereof (e.g., acetic, propionic,hydroacetic, adipic, succinic, benzoic) and inorganic acids (e.g.,hydrohalo, boric). The adduct-forming reaction is normally verystraightforward, involving mixing together the respective components andcreating the resultant adduct. Many such reactions are slightlyexothermic.

The adducts of the invention can be used in either solid (e.g., pellets,balls, sticks, or powders) or liquid dispersion form. In the case ofsolids, the adduct(s) can be mixed using a high intensity mixing device,followed by forming discrete, solid bodies. If desired, a minor amountof an anti-caking agent may be added to facilitate handling, e.g., up toabout 5% (and usually no more than about 1%) by weight of an agent suchas sodium silico aluminate, based upon the total weight of thecomposition exclusive of anti-caking agent taken as 100% by weight. Forease of use, however, the amine adducts of the invention are normallydispersed in water or other aqueous liquids, typically at a level offrom about 1-2.5 lbs. of the solid adduct(s) per gallon of aqueousliquid. Normally, the adducts are readily dispersible in aqueous systemsusing only moderate mixing.

DRAWING

The single FIGURE is a graph summarizing a series of tests usingpreferred amine adducts of the invention for desulfurization of crudeoil.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The amine adducts of the invention, whether in solid or liquid form, arecapable of effecting a substantial desulfurization of liquidhydrocarbons. The hydrocarbons may be of virtually any type, for examplecrude oil and fuels derived from crude oil such as all grades of dieselfuel, jet fuels, and gasolines. However, it is normally desired to treatcrude oil using the amine adducts of the invention to thereby lessen thesulfur loading on downstream refinery processes. Broadly speaking, theamine adducts of the invention are contacted with a selected liquidhydrocarbon in an effective amount to achieve desulfurization, in thepresence of water. The water may be a part of a hydrocarbon-watermixture as in the case of a producing well output, or the water fractionmay be added along with the adduct. The amine adducts should becontacted with liquid hydrocarbons at a level of from about 100-50,000ppm (more preferably from about 250-20,000 ppm or 250-10,000 ppm, andmost preferably from about 300-2,000 ppm) amine adduct per ppm of totalsulfur in the liquid hydrocarbon.

In the case of crude oil, contact between the amine adducts of theinvention and the crude can most advantageously be made simply bydropping or injecting the amine adduct material directly into aproducing well, and specifically into the annulus and/or producing zoneof the well. A recycled side stream of well fluid is also injected whichhelps assure that the amine adducts reach the bottom of the well.Normally, downhole temperatures are greater than ambient surfacetemperatures, and it has been found that such higher temperaturesaccelerate the desired desulfurization. The unwanted sulfur material isseparated into the water phase of the well fluid and can thus be readilyhandled and disposed of by conventional means.

In other treatment applications such as in well field tanks andseparators, and in transmission pipelines and in refinery processing,the amine adducts are added to the liquid hydrocarbons with mixing, ifpossible, such as through the use of static mixers, agitators, orultrasound treatment. Where possible, elevated temperatures of fromabout 100-180° F., more preferably from about 120-160° F., should beachieved during contact between the amine adducts and the liquidhydrocarbons, e.g., the liquid hydrocarbon should be heated to theselevels.

In preferred forms, the amine adduct desulfurization compositions areadded during pipeline transport and/or refinery treatment of a liquidhydrocarbon. In this context, the compositions may be added at oneinstance, substantially continuously or at less frequent intervals. Inanother preferred method, the compositions of the invention are added toa producing well for desulfurization of crude. In this mode of use, thecompositions are added substantially continuously, e.g., by continuouslymetering an appropriate amount of the desulfurization composition intothe well. As used herein, however, “substantially continuously” withreference to addition of desulfurization composition(s) is intended toembrace continuous metering as described as well as less frequentadditions, but typically at least twice per day.

In all instances, however, the adducts of the invention should becontacted with the liquid hydrocarbon in the presence of water. Watershould be present at a level of at least about 1% by weight, and morepreferably at least about 5% by weight. Considering the situation wherea water-hydrocarbon mixture is treated, the hydrocarbon fraction shouldbe present at a level of at least about 50% by weight, and morepreferably at least about 80% by weight. In particularly preferredforms, the hydrocarbon and water fractions form a hydrocarbon-wateremulsion.

The presence of water with the hydrocarbon in the methods of theinvention is believed to facilitate removal of sulfur from thehydrocarbon and to partially solubilize the sulfur in the water. Indeed,attempts to use the adducts of the invention in the absence of waterhave generally given very poor desulfurization results.

The compositions and methods of the invention can commonly achievedesulfurization by removal of elemental sulfur, sulfur complexes, and/orsulfur-bearing compounds such as thiophenes; levels of sulfur reductionof at least about 25%, and more preferably from about 40-70%, can beobtained.

EXAMPLE 1

In this example, a preferred amine adduct was prepared and used todesulfurize Saudi crude oil having a sulfur content of 3.16%.

The amine adduct was prepared by mixing together 20% by weight of solidbenzoic acid and 80% by weight of liquid coco-1,3-diaminopropane,followed by moderate mixing. The reaction was slightly exothermic. Next,2.5 gms. of the resultant adduct product were added to 30 ml. of water,and this aqueous dispersion was added to 120 ml. of Saudi crude oil. Theoil/aqueous adduct mixture was then placed in a separatory funnel whichwas shaken vigorously approximately 100 times. The hydrocarbon andaqueous phases were then allowed to separate, and the hydrocarbonfraction was drawn off and analyzed to determine total sulfur content.The treated hydrocarbon fraction exhibited a sulfur content of 2.32%,constituting a 26.5% sulfur reduction.

EXAMPLE 2

The desulfurization test of Example 1 was repeated using 6 additionalamine adduct products. Specifically, each amine adduct was prepared byreacting coco-1,3-diaminopropane with glacial acetic acid (Sample A),propionic acid (Sample B), boric acid (Sample C), hydroacetic acid(Sample D), adipic acid (Sample E), and succinic acid (Sample F). Therespective samples were dispersed in 30 ml. water, and the resultingdispersions were added to 120 ml. of Alaskan crude oil. Theabove-described separatory funnel treatment was then carried out on eachoil sample.

The results of this series of tests are set forth in FIG. 1. Asillustrated, the untreated oil had a sulfur content of 0.905% and thetreatment according to the invention resulted in a reduction in sulfurcontent of from about 49.2 to 66.4%.

EXAMPLE 3

In this example, Alaskan crude oil having a sulfur content of 0.894% wasmixed with distilled water at varying percentages, and the resultingmixtures were each treated with 25 gms. of the amine-benzoic acidcomposition of Example 1 in 100 ml. of water. The test protocol ofExample 1 was then carried out on each sample, giving the followingresults: Oil Aliquot Mixing Sulfur Content % Sulfur (ml) Water (ml) (ml)Temp (° F.) (wt. %) Reduction 120 0 10 120 0.340 62 120 10 10 120 0.23573.7 120 20 10 120 0.525 41.3 120 30 10 120 0.252 71.8 120 50 10 1200.232 74.0

1. A method of reducing the content of sulfur and/or sulfur-bearingcompounds in liquid hydrocarbon during pipeline transport and/orrefining thereof, said method comprising the step of contacting thehydrocarbon with an effective amount of a desulfurization compositionand in the presence of water during said pipeline transfer and/or saidrefining, said composition comprising the adduct reaction product of anamine and an acid, and separating some of the sulfur or sulfur-bearingcompounds from said liquid hydrocarbon.
 2. The method of claim 1, saidamine adduct selected from adducts of amines of the formulaR—(NR₁—(CH₂)_(n)—NHR₂)_(x) where R is selected from the group consistingof aryl, alkyl, cycloalkyl, arylalkyl, alkoxyalkyl, hydroxyalkyl, andalkoxyhydroxy groups and wherein the alkyl groups or moieties areselected from the C2-C24 alkyls, R₁ and R₂ are individually selectedfrom the group consisting of H and C1-C4 alkyls, n is from about 2-12,and x is from about 1-8
 3. The method of claim 2, said adduct comprisingthe reaction product of a fatty acid amine and an acid.
 4. The method ofclaim 3, said fatty acid amine being a C8-C24 fatty acid amine.
 5. Themethod of claim 4, said fatty acid amine being coco-1,3-diaminopropane.6. The method of claim 3, said acid comprising benzoic acid.
 7. Themethod of claim 1, said composition being in the form of an aqueousdispersion.
 8. The method of claim 7, said aqueous dispersion comprisingof from about 1-1.5 lbs. of said composition per gallon of aqueousliquid.
 9. The method of claim 1, said composition being contacted withsaid liquid hydrocarbon at a level of from about 100-50,000 ppm of theadduct per ppm of total sulfur in the liquid hydrocarbon.
 10. The methodof claim 9, said level being from about 250-10,000 ppm.
 11. The methodof claim 10, said level being from about 300-2,000 ppm.
 12. The methodof claim 1, said composition consisting essentially of said adduct. 13.The method of claim 1, said hydrocarbon being in a flowing stream withwater, said method including the step of substantially continuouslymetering amounts of said composition into said flowing stream.
 14. Themethod of claim 1, said liquid hydrocarbon and water forming anoil-water emulsion, said composition being added to said emulsion. 15.The method of claim 1, said hydrocarbon being mixed with water to form amixture, said mixture comprising at least about 50% by weight liquidhydrocarbon.
 16. The method of claim 15, said mixture comprising atleast about 80% by weight liquid hydrocarbon.
 17. A method of reducingthe content of sulfur and/or sulfur bearing compounds in crude oilduring operation of a crude oil well yielding a mixture including crudeoil and water, comprising the steps of substantially continuously addinga desulfurization composition into the well during said operationthereof, said composition comprising an adduct derived from the reactionbetween an amine and an acid, and separating at least a portion of saidwater from said liquid hydrocarbon after said addition step.
 18. Themethod of claim 17, said composition being added by substantiallycontinuously metering the composition into the well.
 19. The method ofclaim 17, said composition being added intermittently to the well, witha frequency of at least twice per day.
 20. The method of claim 17, saidadduct selected from adducts of amines of the formulaR—(NR₁—(CH₂)_(n)—NHR₂)_(x) where R is selected from the group consistingof aryl, alkyl, cycloalkyl, arylalkyl, alkoxyalkyl, hydroxyalkyl, andalkoxyhydroxy groups and wherein the alkyl groups or moieties areselected from the C2-C24 alkyls, R₁ and R₂ are individually selectedfrom the group consisting of H and C1-C4 alkyls, n is from about 2-12,and x is from about 1-8
 21. The method of claim 17, said adduct being anadduct of a fatty acid amine and an acid.
 22. The method of claim 21,said fatty acid amine being a C8-C24 fatty acid amine.
 23. The method ofclaim 22, said fatty acid amine being coco-1,3-diaminopropane.
 24. Themethod of claim 21, said acid comprising benzoic acid.
 25. The method ofclaim 17, said composition being in the form of an aqueous dispersion.26. The method of claim 25, said aqueous dispersion comprising fromabout 1-1.5 lbs. of said composition per gallon of aqueous liquid. 27.The method of claim 17, said composition being contacted with saidliquid hydrocarbon at a level of from about 100-50,000 ppm of the adductper ppm of total sulfur in the liquid hydrocarbon.
 28. The method ofclaim 27, said level being from about 250-10,000 ppm.
 29. The method ofclaim 28, said level being from about 300-2,000 ppm.